1. Field of the Invention
The present invention relates to a process for manufacturing a laminated glass window, intended, in particular, for automobiles, which reflects infrared radiation and has a layer for sealing the edges.
2. Discussion of the Background
EP-A2-0,391,165 discloses (in connection with U.S. Pat. No. 4,368,945) a process for manufacturing a laminated glass window that reflects infrared radiation, by using multilayer laminated plastic containing a metallic layer responsible for reflecting infrared radiation, as well as a sealing placed on the edges, in order to protect the metallic layer, silver is generally used. As for the metallic layer reflecting infrared radiation. This conventional laminated glass window is manufactured according to the normal process from laminated plastic and the two glass sheets. The laminated plastic extends to the edges of the laminated glass window. The sealing occurs by placing a waterproof adhesive product on the "section" (i.e., the edge) of the permanent laminated glass window. In order to form this adhesive layer for sealing the edges, thermoplastic adhesive material with a base of polybutylene copolymers, glues with a base of fluorine polymers, or glues with a butylene base are used.
This conventional process is well adapted to the manufacturing of stationary automobile windows (i.e., windows that are installed rigidly in the frames that surround them and whose edges are covered because they are inserted in the frames), but it is not always appropriate, for example, for manufacturing retractable side windows. In fact, since the retractable windows are exposed when the window is open, the adhesive materials are not only visible, but they are also subject to mechanical constraints that may cause destruction of the sealing of the edges.
Patent DE-Al 2,344,616 mentions a means that permits joining a carrier sheet, made of polyethylene terephthalate (PET) and equipped with a conducting layer, to two glass sheets, by means of thermoplastic polyvinylbutyral sheets for the manufacturing of windshields equipped with electrical heating and made of laminated plastic. This eliminates the risk of corrosion of the edges, by partially removing, over a width of 3 to 12 mm, the metallic covering present on the PET sheet which extends to the edges of the glass sheets. This partial removal of the layer can take place by means of chemical or mechanical processes. In this area of the edges, in which the layer has been suppressed, the polyvinylbutyral sheet is directly joined to the surface of the PET sheet and thus plays a necessary role in sealing.
It is also well known that it is possible to prevent corrosion of the silver layer by using a carrier sheet equipped with a covering and having dimensions less than those of the glass sheets. This carrier sheet is wrapped between two thermoplastic sheets whose dimensions can correspond to those of the glass sheets. The sheets are brought together so that the edges of the carrier sheet equipped with the covering are recessed at least 3 mm from the edges of the glass sheets (U.S. Pat. No. 3,794,809).
The polymer of the thermoplastic sheets covering the carrier sheet is then crosslinked by means of a thermal, high pressure process so as to ensure the desired sealing.
While the two processes described above are effective, they have several deficiencies. They require the use of carrier sheets equipped with a covering. There must be free access at least to the coated side. The carrier sheets must then receive at least one additional sheet, such as a thermoplastic sheet, for example, made of polyvinylbutyral. But, the carrier sheets equipped with an accessible layer have a significant disadvantage. In fact, the sensitive superficial layer is not protected during handling of the carrier sheet equipped with a covering, so that there is a risk of harming and/or dirtying the superficial layer. Unfortunately, such defects would be visible on the laminated glass window once it was completed.